March 18, 2013

Roosters Cock-A-Doodle-Doo Because Of Genes Not Light

Some of the finest minds in Japan have finally unlocked one of the world´s greatest mysteries. Animal physiology researchers Tsuyoshi Shimmura and Takashi Yoshimura of Nagoya University in Japan have said they now understand what stirs a rooster to crow in the morning, and it´s not the sun.

Farmers have relied on roosters as mother nature´s alarm clock for centuries, but it was never fully understood if these animals crowed because the sun woke them up or if they instinctively knew it was morning. According to Shimmura and Yoshimura, these animals operate on a kind of circadian rhythm which keeps them in sync with the world around them. Now, the team hope this little discovery will help them understand even more about the genetically modified behaviors of other animals.

“℠Cock-a-doodle-doo´ symbolizes the break of dawn in many countries,” said Yoshimura in a press statement. “But it wasn´t clear whether crowing is under the control of a biological clock or is simply a response to external stimuli.”

This stimuli could be anything from the rising sun to the bright burst from car headlights and even another rooster´s crow. To get to the bottom of this behavior, the team had to first remove any distractions which might cause roosters to crow early.

To conduct their research, the team placed three groups of four birds in specially lit and soundproof rooms. These birds were first subjected to cycles of 12 hours of light representing daytime and 12 hours of dark, representing night. Once the roosters caught the rhythm, they began to crow about two hours before the lights were turned on.

To really put this theory to the test, Shimmura and Yoshimura then subjected the birds to 24 hours of dark and quiet solitude – no lights, no sounds. Surprisingly, the roosters continued to crow about two hours before “daylight,” or before the lights had previously been turned on during the beginning stages of the test.

Next, the researchers placed some external stimuli in the cages such as lights and sounds. While these stimuli did rouse the birds and get them to crow ahead of their 'two-hour-before-dawn' timeframe, they were still more likely to call earlier in the day. This means, according to the researchers, that the birds operate on a circadian rhythm.

While the mystery of when and why a rooster crows has eluded scientists for centuries, Shimmura and Yoshimura say that a rooster´s call is a mystery unto itself.

Unlike human speech or other bird calls, a rooster´s crow is not something that´s learned or handed down from the generations. Roosters are inherently born with the ability to crow at the rising sun and now, these researchers believe the time at which they call is also built into their brains.

“We still do not know why a dog says ℠bow-wow´ and a cat says ℠meow,´” Yoshimura said in the statement. “We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model.”

The research is published in the March 18 issue of the journal Current Biology.